A number of diseases are known which are associated with demineralization or mineralization disorders of bone. The most well-known disease is without doubt osteoporosis, in which the regeneration of the bone tissue is imbalanced because the breakdown of the bone matrix by the osteoclasts becomes predominant. The activity of the osteoblasts is greatly decreased and, as the disease progresses, the inorganic matrix is present in an insufficient quantity to allow activity of the osteoblasts to develop normally. The result of this is that the reconstruction of the bone matrix is interrupted or, in any case, insufficient to maintain the conditions necessary for the osteogenesis process. The number, thickness and relative volume of the bone-tissue bridges in the spongy bone are reduced. The density of the bone decreases, which leads to greater mechanical fragility. This results in bone fractures due to impact or falling (especially fractures of the femur, of the wrists or of the humerus) or else vertebral compressions under the pressure exerted by the weight of the body. Repairing such fractures may become difficult because of the small mass of bone available for repair. It is known, in particular, that fractures of the neck of the femur in the elderly suffering from osteoporosis can lead to death in approximately 20% of cases.
Other diseases are accompanied by demineralization or weak mineralization or a mineralization defect of the bone. This is the case, in particular, of Paget's disease, fibrous dysplasias and osteodystrophies caused, in particular, by certain renal insufficiencies. In addition, demineralization of the jaw bone may be the cause of certain periodontal diseases.
Until now, the treatments of demineralization diseases of the bone, in particular osteoporosis, comprise oral supply of calcium, optionally in association with vitamin D, or the administration of oestrogens, optionally in combination with progestogens. These treatments can arrest the breakdown process, but without allowing remineralization by regeneration of the interstitial bone tissue.
The administration of fluorides, also orally, stimulates the osteoblast activity and can lead to an increase in the bone mass by 5 to 10% per year in responsive patients (approximately 60% of cases). However, treatment using fluorides has the drawback of some degree of cumulative toxicity, with the appearance of bone microfractures which can cause significant amounts of pain.